Voltage regulating transformer systems



Jan. 2, 1968 r SOLA 3,361,956

VOLTAGE REGULATING TRANSFORMER SYSTEMS Filed Dec. 16, 1963 4Sheets-Sheet l AND CONTROL UNIT SENSING INVENTOR. g/o SEPH G4 Sou? NEW 44,222

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INVENTOR ATTORNEYE United States Patent 3,361,956 VULTAGE REGULATINGTRANSFORMER SYSTEMS Joseph G. Sela, River Forest, 111., assignor toBasic Products Corporation, Elk Grove Village, 111., a corporation ofWisconsin Filed Dec. 16, 1963, Ser. No. 330,813 9 Claims. (Cl. 323-45)This invention relates to electric regulators and especially to linevoltage regulators.

Among the problems of previous line voltage regulators has been the useof moving parts, the relatively slow response thereof to changes in linevoltage and load, and sensitivity of the regulator to frequency changeand waveform distortion. Previous types of line voltage regulators havein many instances relied upon motor driven variable ratioautotransforrners for maintaining a prescribed output voltage value whenline voltage and load changes occur, such motor driven devices beingslow in operation and requiring moving parts which are subject to wear.Ferro-resonant type line voltage regulators are generally restricted topower sizes of the order of kva. and less and are inherently sensitiveto the frequency of the applied voltage. Also, there will be a change inoutput Voltage with frequency changes. Furthermore, although they can beadjusted to have good regulation for changes in line voltage, theycannot also be adjusted for satisfactory regulation for changes in loadimpedance. Additionally, they produce waveform distortion which may ormay not require external filtering for correction. Previous types ofstatic regulators using saturable devices, such as magnetic amplifiersor semiconductor devices (e.g., controlled rectifiers), operate bygating portions of the line voltage from a load. Although their responsemay be fast and the devices static, they can produce undesirabledistortion of the output voltage requiring bulky, expensive and externalfiltering.

One of the objects of the present invention is to provide a regulatingtransformer which has relatively fast response, good output waveform,and requires no moving parts.

Another object of the invention is to provide an arrangement wherein thematerial and parts required per kva. of regulated power is relativelysmall compared with previous static devices.

In one aspect of the invention, an A.C. source is pro vided with atleast two A.C. magnetic circuits, each circuit having an A.C. mainwinding means and an auxiliary winding means connected in seriestherewith. In one form, only one of the AC. winding means has anauxiliary winding means associated therewith and at least one of themagnetic circuits has a DC. saturating means. One of the magnetic meanshas an air gap located in a portion thereof in such a manner that itwill affect only the A.C. flux produced by the winding means. The airgap serves to reduce the cyclic variation of the reluctance for thecircuit concerned. Preferably, each A.C. winding means has an auxiliarywinding associated therewith, one being in boost relation and the otherin bucking relation. A DC. saturating means is provided for both.

In another form of the invention, the magnetic circuits can be locatedon a single core in which case the shunt does not necessarily require anair gap therein. It is preferred, however, that an air gap be employedso as to obtain minimum distortion and adequate regulation. For bestperformance, the auxiliary winding turns should be so related to thecore area cross section that with maximum output to the load, the corewill operate below saturation. It is desirable that the harmonic contentof the output be not more than about 3% when a sine wave source isemployed.

In one form of core structure, the shell has a center leg withbifurcated ends, the bifurcated ends having the DC. saturating windingthereon. The shunt means is located near the center of the center leg,and the main winding means with its auxiliary winding means is locatedon either side of the shunt.

The DC. saturating means can be connected to a suitable control circuitresponsive to the output voltage. It may control the saturating windingstogether or only one at a time. The device is dependent upon D.C.saturation of either half of the magnetic core means. When no DC. isimpressed upon the saturating means, the input voltage divides betweenthe two primary or main winding means. If DC. is applied to only onepart of the magnetic structure, the input voltage is transferred to themain winding of the other part of the magnetic structure, so that thevolts per turn of the auxiliary winding on the part having DC. appliedwill .be reduced while the volts per turn of the auxiliary winding onthe unsaturated part increase. As one auxiliary winding voltage aids theinput voltage and the other opposes, the output voltage will becontrolled by application of DC. to the desired portion of the magneticstructure.

These and other objects, advantages and features of the invention willbecome apparent from the following description and drawings which aremerely exemplary.

In the drawings:

FIG. 1 shows a schematic wiring diagram;

FIG. 2 shows one form of the invention;

FIG. 3 shows another form of the invention;

FIG. 4 shows a still further form of the invention;

FIG. 5 is a graph showing the relation between k and percentage of thirdharmonic at 54,000 lines per square inch input flux density; and

FIG. 6 is a still further form of the invention.

Referring to FIGS. 1 and 2, in one embodiment of the invention, the mainwinding comprises at least a pair of windings 10, 11 on core means 12.Auxiliary windings 13, 14 are connected to the main windings 10 and II.The shunt 14A is schematically shown as located between main windingportion 11 and its auxiliary winding 14 and main winding 10 and itsauxiliary portion 13. The auxiliary windings 13 and 14 are arranged sothat one will be in bucking relation to the load and the other in aidingrelation to the load. The source of A.C. 33 is connected across leads15, 16 to points 17 and 18 between main winding means 10, I1 and 13, 14.When the windings are on a single core, the shunt may be solid, but itis preferable that there be an air gap therein so as to provide minimumdistortion.

At least one end of core 12 is arranged to have DC. control Windingmeans 19, 20 associated therewith for the purpose of saturating orcontrolling the saturation of that portion of the core. It is preferableto use a second DC. control winding arrangement 21, 22. The DC. controlwinding means may be controlled by a sensing and control arrangement 23,which is connected across load 24, the sensing and control means 23being any conventional means. The load is connected across the outerends of auxiliary windings 13 and 14 by leads 25 and 26.

Referring to FIG. 2, the core means 27 may take the form of a shellalthough it can take other shapes. The center leg 22} has bifurcated endportions 29, 30 at each end thereof. The DC. control windings 21 and 22are on the bifurcated portions of end 29 and the DC. control windings 19and 20 are on the bifurcated end portion 3t), each pair being in opposedrelation.

The auxiliary windings 13, 14 are shown in heavier lines for clarity indescription. Main windings 1t) and 11 are connected together by means ofa lead 31, and shunt means 32 and 33A are located between the mainwinding means 10 and 11. The source 33 is connected by means of leads15, 16 to points 17, 18 of the main winding means and load 24 isconnected by means of leads 25 and 26 to the ends of the auxiliarywinding means 13 and 14, respectively.

Describing the operation of the arrangement shown in FIG. 2, A.C. isapplied to the main windings 10 and 11 from source 33, causing a flux toexist in the center legs 34, 35 of the core. These fluxes may not beequal in magnitude or in phase, the difference fluxes passing throughshunts 32, 33A. With no control current applied to the DC. windings oneither side, line voltage 33 -is substantially passed to the load 24without appreciable change in magnitude. When DC. is applied to controlwindings 19, 20, the portion 35 of the core becomes saturated and thesource voltage 33 then appears mainly on main winding 10, producing aflux through core section 34 and the shunt so as to energize onlyauxiliary winding 13. Since auxiliary winding 13 is connected inboosting relation, the result is that the load voltage at 24 rises to avalue above the source voltage 33. On the other hand, if control currentis applied to control windings 21 and 22, portion 34 of the core becomessaturated and the line voltage 33 is now applied to main winding 11, sothat the flux passes through portion 35 and through shunts 32 and 33A toenergize auxiliary winding 14. Since auxiliary winding 14 is connectedin bucking relation, the load voltage at 24 becomes less than the linevoltage 33. By suitably controlling the currents in the DC. windings,the relationship between the line voltage 33 and load voltage 24 can bevaried over the range of boosting and bucking turns ratios determined bywindings 13 and 10 and windings 11 and 14.

Merely by way of example, referring to FIG. 2, the core for a kva.regulator may be 3 /2 inch stack of 29- gauge laminations M-lS hotrolled steel. The longitudinal dimension may be 8" and the crossdimension 7". The center or middle core is 3%. wide and is locatedbetween the two end legs. The bifurcated portion has an opening orwindow of 1%" width by 1% thick. The shunts are one inch wide and arelocated between the center portion and the outer legs with a gap of0.010 between each shunt and the shell. The main windings each have 57turns, and the "boosting auxiliary winding has 12 turns. The auxiliarybucking winding for bucking has 2 turns. The control windings each have112 turns.

The aforementioned regulator maintained a constant output voltage of 115volts at 60 c.p.s. for a range of input voltage from 104 to 127 volts.The maximum percentage of harmonics of the output voltage has a thirdharmonic of 3.6% of the fundamental at the maximum line voltagecondition and at full load. With an air gap in the shunt of 0.025", themaximum value of the third harmonic was 2.7% of the fundamental of theoutput voltage at the maximum line voltage condition and at full load.

In FIG. 3, a pair of cores 100, 101 having main windings 102, 103 areshown. Auxiliary windings 104 and 105 are connected to the ends of mainwindings 102 and 103, and the load 1.06 is connected to terminal 107 and100A of the auxiliary windings. The D.C. control windings 108 and 109are arranged to be connected to a source of control, DC. The DC. controlwindings preferably are split in two parts, one on each of the twocenter legs. Each core 100, 101 has two center legs, and the outer legshave air gaps 109A, 110, 111 and 112.

Describing the operation of PEG. 3, source voltage 113 is applied to themain windings 102 and 103 in series. With no control current in eitherstructure, the source voltage is passed through the two transformers tothe load 106 without substantial alteration. If control current isapplied to windings 108, the center legs become saturated and the linevoltage 113 now appears mainly across winding 103. Since the windings103 and 105 act in boosting relation, load voltage 106 then rises abovethe line voltage 113. If control current is applied to control winding109, the line voltage will appear across winding 102 and since windings102 and 104 are connected in bucking relation, the load voltage 106 willbe forced below the line voltage 113. By adjusting the control currentin windings 108 and 109, a range of relationships between line and loadvoltage can be obtained within the turns ratio limits of the main andauxiliary windings on the two structures.

FIG. 4- shows a still further form of the invention wherein shells 120,121 have interiorly disposed cores 122, 123, respectively. The shellsand cores may be so dimensioned that the desired air gaps in the shuntswill be at 124, 125, 126, 127. The A.C. source is connected across mainwindings 12 8, 129 by leads 130, 131, the main windings being seriallyconnected together by lead 132. The boost auxiliary winding 133 isconnected in series with the load 1.34 by lead 135 and with its mainwinding by lead 136. Bucking auxiliary winding 137 is connected to load134 by lead 135A and with its main winding 129 by lead 138.

The DC. control windings 139 and 140 are wound on the center cores only,said windings being suitably con nected to the DC. control circuits.

The arrangement of FIG. 4 Will operate in a manner similar to thepreviously described forms.

Referring now to the embodiment having an air gap, regulation will bedependent upon the DC. ampere turns, the air gap in the shunt and thenumber of aiding and opposing turns. The regulating range increases asthe number of DC. ampere turns increases.

It has been found that the regulating range decreases as the air gapincreases. Thus, when the air gap increases, from no gap to a 0.050"gap, the regulating range decreases to less than one half its range atno gap. The regulating range increases as the number of aiding andopposing turns increases. However, the increase in range for a givenincrease in turns becomes less as more turns are added.

In the form where auxiliary windings are wound directly over the mainwindings, the leakage reactance will be ery low. Because of the closecoupling of the main and auxiliary windings, the line power factor isvery high, and may be 97% or better.

It was ascertained that the total harmonics can be held under 3% for aninput regulating range of 110% of nominal voltage. It appears that thereare two primary sources of harmonics, A.C. saturation caused by theauxiliary winding ampere turns and 'by a certain combination of mainwinding and DC. flux. The major portion of the output distortion iscaused by the third harmonic voltage. The third harmonic voltage, causedby auxiliary winding A.C. saturation, is a maximum when no D.C. flux ispresent in the core, the amount of third harmonic voltage distortion inthe output being dependent upon such A.C. saturation level.

The following relationship gives the auxiliary winding current requiredto produce a particular percentage of third harmonic output voltage:

The value of k depends upon the percentage of third harmonic outputvoltage. L is the inductance of the auxiliary windings in series.

Thus tang =3.19N2A 10B I=Load current in amps.

N =Number of aiding and opposing turns A =Net cross section of the corein square inches L zLength of air gap in inches L =Length of magneticpath of core in inches ,u=Etfective permeability of the coreL=Inductance in henrys k=Third harmonic content factor (see FIG. 5

From the above equation, it is possible to determine the maximum loadcurrent which will produce less than a 3% third harmonic voltage in theoutput. For 3% third har monic voltage k=.03.

The values of k, shown in FIG. 5, are for a fixed input fiux density. Ifthe input flux density is increased, k increases slightly, thus allowinglarger load current for the same percentage of third harmonic voltage.If the input flux density is reduced, the value of k decreases, thusallowing less load current for the same percentage of third harmonicvoltage.

It is difficult to analyze the second source of harmonics which iscaused by a combination of primary and DC. flux. It is dependent uponthe input flux density, the air gap and the number of aiding andoppoisng turns. The output harmonic voltages under these conditions area maximum, when half of the core under the aiding winding is partiallysaturated with DC. For this condition the output harmonics increasedirectly as the opposing turns increase. The harmonics increase as theinput flux density increases and decreases .as the air gap is increased.

The'form shown in FIG. 6 is a five legged core arrangement 150, thecenter leg 151 having air gap 152, theouter legs having D.C. windings153, 154 on each of the outer legs 155, 156 and 157, 158 respectively.The outer legs are also wound with A.C. windings over the legs two at atime, the primary windings 159 and 160 being Wound around legs 155, 156and 157, 518 respectively. The primary windings are series connected bylead 160A and to the source 161A, the source being connected to leads163, 164. The bucking or opposing winding 165 also is wound on legs 157,158 in the same direction as the A.C. winding and is connected to theA.C. winding at point 162. The boost or aiding winding 165A is connectedat point 161 to the A.C. winding on legs 155, 156. The opposite end ofthe bucking winding is connected by lead 166 to one portion of theoutput or load 166A. The opposite end of boost winding 165A is connectedby lead 167 to the other side of the output 166A. The DC. windings 153and 154 are connected to a DC. control means (not shown) as previouslydescribed. The direction of DC. winding 153 is such that the DC. ampereturns produced by the winding on the two legs 155, 156 are in adirection to produce saturation of legs 155, 156. Likewise, thedirection of DC. windings 154 on legs 157, 158 is in a direction toproduce saturation of legs 157, 158 without producing a DC. flux in thecenter leg 151.

In the operation of the regulator with neither D.C. winding energized,the input voltage is transferred directly to the output with littlechange in magnitude because the buck and boost winding 165, 165A cancelthe effect of each other. However, if one of the DC. windings, forexample, winding 154, is energized to saturate legs 157, 158, the buckwinding 165 is disabled and the boost winding 165A operates in itsmagnetic circuit. The effect is to produce an increase in the outputvoltage. On the other hand, if D.C. winding 153 is energized to saturatecore legs 155, 156, the boost winding A is disabled and the buck winding165 operates to decrease the outputvoltage over the input voltage.During this operation, the A.C. flux path is shifted from between theouter legs in accordance with the degree of saturation produced by theDC windings. If one of the DC. windings saturates one pair of outerlegs, such as legs 157, 158, the A.C. flux is then confined mainly tothe legs 155, 156, linking the turns 159 of the primary winding andproducing the appropriate voltage in the boost winding 165A. By thismeans, the output voltage can be controlled by applying independent DC.to the DC. saturating windings for a fixed value of primary voltage.Conversely, for varying values of primary voltage, the output voltagecan be maintained constant by suitably controlling the limits of currentin the DC. saturating windings.

It should be apparent that various changes may be made in the details ofthe circuit and structures without departing from the spirit of theinvention except as defined in the appended claims.

What is claimed is:

1. In an A.C. voltage regulator, the combination including load means,an A.C. source, at least two A.C. magnetic circuits, each of saidmagnetic circuits having an A.C. main winding and at least one of saidcircuits having an auxiliary winding connected in series with its mainwinding, at least one of said magnetic circuits having D.C. saturatingmeans, said main winding means being connected serially, meansconnecting said A.C. source across said serially connected main windingmeans, means connected said auxiliary winding means to said load meansand the other side of the load to said other main winding means, atleast one of said magnetic circuits having an air gap located in aportion thereof to affect only A.C. flux produced by the main winding,said air gap serving to reduce the cycling variation of the reluctanceof the circuit in which it is located, and means for applying DC. tosaid saturating means.

2. In an A.C. voltage regulator, the combination including load means,an A.C. source, a pair of A.C. magnetic circuits, each of said magneticcircuits having an A.C. main winding and an auxiliary winding connectedin series with its main winding, said main windings being connectedserially, at least one of said magnetic circuits having D.C. saturatingmeans, said A.C. source being connected across said serially connectedmain winding means, means connected said load across said main windingand auxiliary windings, at least one of said magnetic circuits having anair gap located in a portion thereof to aifect only A.C. flux producedby the main winding, said air gap serving to reduce the cyclic variationof the reluctance of the circuit in which it is located, and means forapplying D.C. to said saturating means.

3. In an A.C. voltage regulator, the combination including load means,an A.C. source, a pair of A.C. magnetic circuits, each of said magneticcircuits having an A.C. main winding and an auxiliary winding connectedin series with its main winding, said main windings being connectedserially, each of said magnetic circuits having D.C. saturating means,said A.C. source being connected across said serially connected mainwinding means, means connecting said load across said main winding andauxiliary windings, at least one of said magnetic circuits hav ing anair gap located in a portion thereof to aifect only A.C. flux producedby the main winding, said air gap serving to reduce the cyclic variationof the reluctance of the circuit in which it is located, and means forapplying DC. to said saturating means.

4. In an A.C. voltage regulator, the combination including load means,an A.C. source, magnetic core means, a pair of main winding means, atleast one of said winding means having an auxiliary winding meansserially connected therewith, air gap shunt means between said mainwinding means, at least one D.C. saturating winding means forcontrolling the saturation of that part of said core means associatedwith at least one of said main winding means, at least part of each ofsaid main Winding means being series connected together and to thesource, parts of said main winding means and said serial- 1y connectedauxiliary winding means being connected across said load means, andmeans for applying DC. to said saturating winding means.

5. In an A.C. voltage regulator, the combination including load means, amagnetic core means having a shell and a center leg with bifurcated endsabutting said shell, magnetic shunt means located between said shell andsaid center leg inwardly of said bifurcated ends, main winding means oneither side of said magnetic shunt means each having an auxiliarywinding means serially connected therewith, means for connecting an A.C.source to a point between each of said main winding means and itsauxiliary winding means, means connecting said load means across saidauxiliary winding means, DC. control winding means on said bifurcatedends, and means for applying DC. to said DC. control winding means.

6. In an A.C. voltage regulator, the combination including load means, amagnetic core means having a shell and a center leg with bifurcated endsabutting said shell, magnetic shunt means with an air gap locatedbetween said shell and said center leg inwardly of said bifurcated ends,main winding means on either side of said magnetic shunt means eachhaving an auxiliary winding means serially connected therewith, meansfor connecting an A.C. source to a point between each of said mainwinding means and its auxiliary Winding means, means connecting saidload means across said auxiliary winding means, DC. control windingmeans on said bifurcated ends, and means for applying DC. to said DC.control winding means.

'7. In an A.C. voltage regulator, the combination including load means,an A.C. source, a single core means providing a pair of A.C. magneticcircuits, each of said magnetic circuits having an A.C. main winding,said main windings being connected serially, an auxiliary windingconnected in series with each main winding, said A.C. source beingconnected across said serially connected main winding means, meansconnecting said load across said main winding and auxiliary windings,D.C. saturating means on said core means, at least one of said magneticcircuits having an air gap located in a portion thereof to effect onlyA.C. flux producedby the main winding, and means for applying DC). tosaid saturating means.

8. In an A.C. voltage regulator, the combination including load means,an A.C. source, a five legged core means having two pairs of legs and acenter leg with an air gap therein, D.C. saturating winding means oneach of said pairs of legs, main winding means on each of said pairs oflegs, said main winding means being serially connected, said A.C. sourcebeing connected across said serially connected main winding means, anauxiliary boost winding means on one of said pairs of legs connected tosaid main winding means and to one side of said load means, an auxiliarybuck winding means on the other pair of said legs and connected to saidmain winding means and said load means, and means for selectivelyapplying DC. to said DC. saturating winding means, energization ofeither one of which shifts A.C. flux to the center leg.

9. In an A.C. voltage regulator, the combination including a shell typecore means providing a pair of A.C. magnetic circuits, each of saidmagnetic circuits being provided with a main winding and a seriesconnected auxiliary winding, one of said auxiliary windings bengconnected in boosting and the other in bucking relationship with respectto its associated main winding, means connecting said main windings inseries, means for connecting said series connected main windings acrossa source of A.C. power, means for connecting said auxiliary windings toa load, and DC. control winding means associated with each of saidmagnetic circuits for controlling the A.C. flux transfer between saidmain and auxiliary windings thereby to control the output voltage tosaid load.

References Cited UNITED STATES PATENTS 1,902,466 3/1933 Ratkovszky 323452,665,406 1/ 1954 Carmichael 32345 2,847,639 8/1958 Howe 32345 2,985,8175/1961 Bird 32356 1,414,652 5/1922 Kirke 32345 1,997,657 4/1935 Schmutz32345 3,172,031 3/1965 Sola 32356 3,188,555 6/1965 Essinger 32389FOREIGN PATENTS 527,536 4/1954 Belgium.

JOHN F. COUCH, Primary Examiner.

W. E. RAY, Assistant Examiner.

1. IN AN A.C. VOLTAGE REGULATOR, THE COMBINATION INCLUDING LOAD MEANS,AN A.C. SOURCE AT LEAST TWO A.C. MAGNETIC CIRCUITS, EACH OF SAID MAGNETIC CIRCUITS HAVING AN A.C. MAIN WINDING AND AT LEAST ONE OF SAIDCIRCUITS HAVING AN AUXILIARY WINDING CONNECTED IN SERIES WITH ITS MAINWINDING, AT LEAST ONE OF SAID MAGNETIC CIRCUITS HAVING D.C. SATURATINGMEANS, SAID MAIN WINDING MEANS BEING CONNECTED SERIALLY, MEANSCONNECTING SAID A. C. SOURCE ACROSS SAID SERIALLY CONNECTED MAIN WINDINGMEANS, MEANS CONNECTED SAID AUXILIARY WINDING MEANS TO SAID LOAD MEANSAND THE OTHER SIDE OF THE LOAD TO SAID OTHER MAIN WINDINGS MEANS, ATLEAST ONE OF SAID MAGNETIC CIRCUITS HAVING AN AIR GAP LOCATED IN APORTION THEREOF TO AFFECT ONLY A.C. FLUX PRODUCED BY THE MAIN WINDING,SAID AIR GAP SERVING TO REDUCE THE CYCLING VARIATION OF THE RELUCTANCEOF THE CIRCUIT IN WHICH IT IS LOCATED, AND MEANS FOR APPLYING D.C. TOSAID SATURATING MEANS.